a) Field of the Invention
The present invention relates to a device for folding a flexible material web having at least one counterrotating pair of laying rollers, between which the material web is feedable to a folding location, the laying rollers being part of a laying carriage which may travel over the folding length of the material web with reversible orientation, the laying wagon including at least two transport bands which rotate around the laying rollers, the material web being transportable at least partially guided between the transport bands, and the speed of the material web having the same absolute value as the speed of the transport bands.
Furthermore, the present invention relates to a method of folding a flexible material web, the material web being fed to at least one folding location via at least one counterrotating pair of laying rollers, the material web being moved together with the laying rollers over their folding length, and an orientation change occurring during the method in accordance with a freely selectable folding length, the material web being transported to the folding position between two transport bands which rotate at least around the laying rollers, and the material web being moved at the same speed as the transport bands.
b) Description of the Related Art
The teaching of the present patent application is based on related art which results from FR 2 739 873. Using the device disclosed therein, first, textile fiber web is compressed between the transport bands into nonwoven having one-dimensional fiber alignment. The transport bands thus not only have a transport function, but also play a role in manufacturing. A receiving band is positioned below the laying rollers, which not only has a transport function, but also has the function of allowing additional orientations of the fibers of the nonwoven coming from the laying rollers. The receiving band is at a constant distance to the exit point of the nonwoven from the laying rollers and moves in the same movement plane at a right angle to the movement direction of the laying carriage, over the width of the nonwoven. In this case, zigzag layers arise at an angle of approximately 45°, which lead to the random fiber position of the nonwoven. Only the folding height changes over the thickness of the material, but not the distance between the receiving band and the laying rollers. This nonwoven having a random fiber position is compacted inline, i.e., in the same production process, to the desired product, specifically to the nonwoven material.
In contrast to this, the present patent application is concerned with the implementation of a stack, starting from a finished product. In other words: in the related art forming the species, a fiber web, a completely uncompacted material coming out of a textile comb, is provided to the transport bands and compaction to the nonwoven then occurs between the transport bands. Using the known device, superposition of nonwoven is generally possible, but the implementation of a stack which is suitable for packaging purposes is not possible. In addition, merely from its manufacturing use aspect, the known device is not suitable for compact folding of a material web.
A folding machine results from DE 91 15 502 U1 which includes a laying slide having laying rollers between which the material web is transported to the folding location. The laying slide may be moved with reversible orientation. The material web is moved together with the laying rollers and/or the slide over a specific folding length which corresponds to the length of a pallet. In the folding machine under discussion, the laying rollers are driven using toothed belts and the material web contacts the rollers and is transported between them. In this case, only one roller is ever driven at a time. In the type of material feed to the folding location under discussion, it is disadvantageous that the speed of the material web and the speed of the one driven roller and the other, non-driven roller may be different and friction is generated in this way. Through these speed differences, mechanical strain, skewing, and electrostatic effects of the material web due to increased friction occur, which may lead to quality losses in the material web and the alignment of the stack, and to wrinkling on the folded stack.
Further relevant related art is formed by DE 198 03 837 A1, which is concerned with the folding and stacking of a flexible web in a zigzag stack. First, a web is typically brought vertically between the rollers. While in contact with the rollers, the particular web section runs in the same rotational direction and rotational speed as the rollers. The step of gripping the web using grippers, which are each positioned on the periphery of a roller, now occurs. The gripping is performed perpendicularly to the movement direction of the web. The rib moves with the web material into the gripper mouth. The gripper mouth closes during the further rotational movement. The rib slides out. Before folding may be performed, the step of letting the material web loose is first to be implemented. The release always occurs at the reversal point of the zigzag layer. The back and forth movement during the folding perpendicular to the movement direction of the arriving web occurs in fractions of seconds. The folding is performed in elevators which are moved downward as the stack grows. Stack changes are performed. The known device may be situated in tandem, so that multiple web widths are operated. The known device is disadvantageous in that the folding length of the web is determined by the dimension of the rollers. The smaller the roller dimensions, the more kinks a web has. Straight kinks may lead to impairment of the fiber properties, as the folded web may still remain for some time in the packed form and, in some circumstances, may be loaded with other web stacks. From a constructive and drive-technology viewpoint, however, the maximization of the roller dimensions is limited. Furthermore, impressions arise on the material due to the gripper mouth mimicry, which may impair the appearance of the material surface. In addition, the gripper mimicry is unsuitable in regard to soft materials, since the yielding nature of the material makes the gripping very difficult or, in the event of a high gripper pressure, strong impressions remain visible in the material. When folding different materials, costly machine adaptation is therefore necessary. Furthermore, relative speed and/or the friction of the web to be folded on the preceding layer occurs during the folding, which may in turn be connected to worsening of the position of the preceding layer, its wrinkling or static charge, or even with quality losses of the materials rubbing against one another.